1. Field of the Invention
The invention relates to metallurgy and more particularly to dummy bars for machines for casting round hollow ingots.
The invention can effectively be employed in horizontal-type machines for continuous casting of round hollow metal ingots.
2. Description of the Prior Art
Billets for manufacturing pipes or other hollow items are currently fabricated generally in vertical-type continuous casting machines. It is common knowledge that these machines require considerably greater investments as compared to horizontal-type continuous billet casting machines. To start casting, use is made of a dummy bar formed with a hollow pipe with bevelled top edges to ensure tightness. The dummy bar is coupled with an ingot being cast by pins sloped to the axis of the ingot and to one another.
There is also known a dummy bar which comprises a head with a central cylindrical orifice for receiving a mandrel and a bar connected to the head by a stud locked by a nut. The head is sealed inside a mould by a bushing from a material generating a gas on contact with molten metal. However, the stud connection of the dummy bar to the head suffers from a shortcoming in that the orifices for the stud on the bar and on the head of the dummy bar fail to coincide when the bar is moved axially by the withdrawal roll unit, as that it is necessary to turn the head of the bar with respect to their axes, this, in its turn, involves problems, as the rotation of the head of the dummy bar inside a mould may break the seal, whereas the bar is prevented from turning by the withdrawal roll unit.